The introduction of an exogenous nucleic acid sequence (e.g., DNA) into a cell, a process known as “transformation,” plays a major role in a variety of biotechnology and related applications, including research, synthetic and therapeutic applications. Research applications in which transformation plays a critical role include the production of transgenic cells and animals. Synthetic applications in which transformation plays a critical role include the production of peptides and proteins, as well as therapeutic RNAs, such as interference RNA or ribozymes. Therapeutic applications in which transformation plays a key role include gene therapy applications.
In many of these applications, it is desirable to introduce the exogenous DNA in a manner such that it provides for long-term expression of the protein or RNA encoded by the exogenous DNA. Long-term expression is primarily achieved through one of two routes: integration of the exogenous DNA into a target cell's genome, or extrachromosomal expression of the exogenous DNA from minicircle vectors. Extrachromosomal expression from minicircles avoids the pitfalls associated with integration, including the accidental interruption of important genes, and the aberrant expression or silencing of the integrated DNA due to the activity at the locus of integration, etc. However, the production of minicircle vectors is a multistep, time-consuming process. What is required is a composition that provides the advantages of minicircle vectors with the ease of preparation of a plasmid.
The present invention addresses these issues.